1. Field of the Invention
The present invention relates to a projector type vehicular headlamp unit that uses a light-emitting element such as a light-emitting diode as a light source.
2. Related Art
A number of projector type vehicular headlamp units that use a light-emitting element such as a light-emitting diode as a light source have been proposed in recent years.
Patent Documents 1 and 2 describe configurations in which such a vehicular headlamp unit is provided with a projection lens arranged on an optical axis that extends in a vehicle longitudinal direction, and first and second light source units arranged rearward of the projection lens.
In the vehicular headlamp unit described in these Patent Documents, the first light source unit includes a first light-emitting element, a first reflector, and a first mirror component. The first light-emitting element is arranged in a vicinity of the optical axis further rearward than a rear-side focal point of the projection lens. The first reflector is arranged so as to cover the first light-emitting element from above and is structured so as to reflect light from the first light-emitting element forward toward the optical axis. The first mirror component has an upward-facing reflective surface that extends rearward generally along the optical axis from a vicinity of the rear-side focal point of the projection lens so as to reflect a portion of the reflected light from the first reflector upward. Lighting the first light source unit forms a first light distribution pattern whose upper end portion has a cut-off line that is an inverted projection image of a front end edge of the upward-facing reflective surface, whereby a low beam distribution pattern or a portion thereof is formed.
According to the vehicular headlamp unit described in Patent Document 1, a second light source unit includes a second mirror component, a second light-emitting element, and a second reflector. The second mirror component has a downward-facing reflective surface that extends diagonally downward toward a lamp rear side from the front end edge of the upward-facing reflective surface of the first mirror component. The second light-emitting element is arranged below the optical axis and faces forward and diagonally downward. The second reflector is structured so as to reflect light from the second light-emitting element upward, with such light generally converging in a region near the rear-side focal point of the projection lens on the downward-facing reflective surface of the second mirror component. The additional lighting of the second light source unit additionally forms a second light distribution pattern above the cut-off line of the low beam distribution pattern, whereby a high beam distribution pattern or a portion thereof is formed.
According to the vehicular headlamp unit described in Patent Document 2, the second light source unit includes the second light-emitting element, a third reflector, and an additional projection lens. The second light-emitting element is arranged facing downward in a vicinity of the optical axis. The third reflector converges and reflects light from the second light-emitting element forward. The additional projection lens is arranged in front of the third reflector. The additional lighting of the second light source unit additionally forms the second light distribution pattern so as to straddle the cut-off line of the low beam distribution pattern from above and below, whereby the high beam distribution pattern or a portion thereof is formed.    [Patent Document 1] U.S. Pat. No. 7,387,416    [Patent Document 2] U.S. Pat. No. 7,311,430